The present invention relates to liquid ejection apparatuses ejecting liquid from a nozzle opening surface of a liquid ejection head, and, more particularly, to liquid ejection apparatuses having liquid wiper devices wiping the liquid from the nozzle opening surface.
As a liquid ejection apparatus ejecting liquid to a target, an inkjet type recording apparatus ejecting ink drops from a recording head to a recording medium for performing printing is known. More specifically, the apparatus ejects ink drops from nozzles of the recording head to the recording medium for defining an image including characters and graphics on the recording medium as desired.
When printing, the recording head of the apparatus is held relatively close to the recording medium. Thus, if the ink drops splash when hitting the recording medium, the ink splash may be received by the nozzle opening surface of the recording head, and the nozzle opening surface may be contaminated.
Particularly, if the apparatus is an on-demand type, the ink drops are ejected through slight pressurization of the ink in the vicinity of each of the nozzles. The ejection energy is thus relatively small, and the recording head must be held at a position as close as several millimeters from the recording medium. Accordingly, the nozzle opening surface easily catches the ink splashes. Further, since only relatively small pressure is applied to the ink, the pressure is insufficient for removing the ink from the clogged nozzles.
Thus, for removing the ink from the clogged nozzles, the apparatus performs ink suction, or draws the ink from the nozzle openings, when the apparatus is not in printing operation.
However, even after the ink suction is performed, the ink may remain in the nozzle opening surface. The remaining ink may cause the nozzle opening surface to be contaminated by fibers from the recording medium, which is a sheet of paper, or by dirt. This may lead to clogging of the nozzles, a failure of ink ejection, or offset ink ejection, as the recording head is repeatedly used.
For solving the problem, a wiper device for wiping the ink from the nozzle opening surface has been proposed, as described in Japanese Laid-Open Patent Publications Nos. 2001-30507 and 11-334090.
Japanese Laid-Open Patent Publications No. 2001-30507 describes a wiper device including a plurality of wiper blades each corresponding to one of nozzle heads ejecting different color inks. Each of the nozzle heads includes multiple nozzles aligned in a main scanning direction. Each of the wiper blades is movable in the main scanning direction. The wiper blades are carried separately by corresponding carriers. Each of the carriers is moved in the main scanning direction through rotation of an associated lead screw. The lead screws are driven independently from each other by corresponding drive sources. This structure makes it necessary to provide the drive sources in the quantity corresponding to the quantity of the wiper blades. Thus, as the quantity of the wiper blades is increased, the mechanism for moving the wiper blades becomes complicated and enlarged.
Further, Japanese Laid-Open Patent Publications No. 2001-30507 describes another wiper device including a plurality of wiper blades carried by a single carrier. The structure decreases the quantity of the lead screws and that of the drive sources, as compared to the quantity of the wiper blades. However, since the carrier moves the wiper blades altogether, the wiper blades wipe the corresponding nozzle heads, regardless of whether the nozzle heads require wiping or not. Therefore, if the nozzle openings of the nozzle head are wiped by the corresponding wiper blade without being subjected to the aforementioned ink suction, so-called missing dots may be caused by the nozzle openings. In this case, the ink cannot be reliably ejected to the recording medium, thus leading to a printing failure.
In contrast, Japanese Laid-Open Patent Publication No. 11-334090 describes a wiper device including a plurality of wiper blades formed of the same material secured to the outer circumference of a rotatable blade support. More specifically, the blade support has a polygonal shape and the wiper blades are secured to each of the sides of the blade support. When a carriage carrying a recording head moves from its home position to a recording area, the recording head slides on one of the wiper blades and is wiped by the wiper blade. Further, by rotating the blade support, the wiper blades may be selected as desired.
However, since the multiple wiper blades are secured to the outer circumference of the blade support, the blade support must be relatively large. Further, since the blade support is rotated in the inkjet type recording apparatus, a relatively large space in the recording apparatus must be ensured specifically for the blade support. This further enlarges the recording apparatus. Also, although the wiper blades can be selected as desired by rotating the blade support, the wiper blades are formed of the same material. This makes it impossible to perform wiping suitably for a current contamination state of the recording head.